This invention relates to electronic apparatus having a tone generating function and, more particularly, to an electronic apparatus having an automatic performance function of progressively producing a series of tones.
Recently, small size electronic apparatus having a tone generating function of effecting automatic performance of a simple melody or permitting performance of a simple melody using ten keys and function keys, for instance an electronic desk-top calculator, have been developed. Further, the tonal character of the generated musical sound is controlled through envelope control of ADSR (attack, decay, sustain and release) portions.
In one type of envelope control in a prior art small size electronic apparatus for performance of a melody with the operation of note keys, constant envelope control is always made irrespective of the "on" and "off" periods of keys. According to this prior art system, however, the tonal character of the generated musical sound is always constant, which is undesired from the musical standpoint. In another system, the envelope control is effected by taking the lengths of the "on" and "off" periods of keys into consideration. In this system, rich and satisfactory tonal characters are available for imparting them to the generated musical sound. On the demerit side, however, when permitting automatic performance of a melody with this system the "on" and "off" periods have to be stored as independent data in the tone memory. Therefore, at least double the storage capacity of the tone memory compared to the first-mentioned system is necessary.
Still further, there have recently been developed small size electronic musical instruments having a so-called one-key play function, in which only note data of a melody is stored in a memory and is read out progressively therefrom every time a particular key is operated, with tone duration data being added to each read-out note data to produce musical sounds, and also small size electronic musical instruments of so-called auto play function, in which both note data and tone duration data of a melody are stored in a memory and are progressively and automatically read out for melody performance.
As the method of coupling note data and tone duration data to a memory in a small size electronic musical instrument having the aforementioned auto play function, there have been proposed one, in which note data and tone duration data are keyed in by actually playing note keys, and one, in which note keys and tone duration keys are alternately operated to alternately couple note data and tone duration data. In the first-mentioned method, however, melody has to be actually performed, and this keying method is difficult for beginners. In the second method, it is necessary to provide note keys, and this increases the size of the instrument.